Low voltage detection circuit and memory device including the same

ABSTRACT

In a low voltage detection circuit having improved detection performance, the low voltage detection circuit includes: a comparison voltage generator for generating a first comparison voltage and a second comparison voltage having a level higher than that of the first comparison voltage by dividing a power voltage; a first comparator for outputting a low voltage detection enable signal by comparing the first comparison voltage with a reference voltage; a second comparator for outputting a detection signal by comparing the second comparison voltage with the reference voltage while the low voltage detection enable signal is being input; a detection signal maintainer for providing a low voltage detection signal to an output terminal according to the detection signal; and an output signal discharger for discharging the low voltage detection signal according to the low voltage detection enable signal.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. §119(a) toKorean patent application number 10-2018-0027536, filed on Mar. 8, 2018,the entire disclosure of which is herein incorporated herein byreference in its entirety.

BACKGROUND 1. Field of Invention

Various embodiments of the present disclosure generally relate to anelectronic device. Particularly, the embodiments relate to a low voltagedetection circuit and a memory device including the same.

2. Description of Related Art

A storage device stores data under the control of a host device such asa computer, a smart phone, or a tablet PC. The storage device mayinclude a memory device for storing data and a memory controller forcontrolling the memory device. The memory device may be a volatilememory device or a nonvolatile memory device,

In a volatile memory device, stored data is not retained when the powersupply is interrupted. Examples of the volatile memory are a StaticRandom Access Memory (SRAM), a Dynamic RAM (DRAM), a Synchronous DRAM(SDRAM), and the like.

In a nonvolatile memory device, stored data is retained even when thepower supply is interrupted. Examples of the nonvolatile memory are aRead Only Memory (ROM), a Programmable ROM (PROM), an ElectricallyProgrammable ROM (EPROM), an Electrically Erasable and Programmable ROM(EEPROM), a flash memory, a Phase-change RAM PRAM), a Magnetic RAM(MRAM), a Resistive RAM (RRAM), a Ferroelectric RAM (FRAM), and thelike. The nonvolatile memory device may include a low voltage detectioncircuit for sensing a voltage drop of a power voltage input from anexternal power supply.

SUMMARY

Embodiments provide a low voltage detection circuit having more accuratedetection performance and a memory device including the same.

According to an aspect of the present disclosure, there is provided alow voltage detection circuit including: a comparison voltage generatorconfigured to generate a first comparison voltage and a secondcomparison voltage having a level higher than that of the firstcomparison voltage by dividing a power voltage; a first comparatorconfigured to output a low voltage detection enable signal by comparingthe first comparison voltage with a reference voltage; a secondcomparator configured to output a detection signal by comparing thesecond comparison voltage with the reference voltage while the lowvoltage detection enable signal is being input; a detection signalmaintainer configured to provide a low voltage detection signal to anoutput terminal according to the detection signal; and an output signaldischarger configured to discharge the low voltage detection signalaccording to the low voltage detection enable signal.

According to another aspect of the present disclosure, there is provideda memory device including: a memory cell array including a plurality ofmemory cells; a voltage generator configured to generate an operationvoltage to be supplied to the plurality of memory cells; and controllogic configured to provide the operation voltage to the plurality ofmemory cells or discharge the provided operation voltage, wherein thevoltage generator further includes a low voltage detection circuitconfigured to output a low voltage detection signal to the control logicwhen a power voltage input from the outside corresponds to a low voltagestate, wherein the low voltage detection circuit includes: a comparisonvoltage generator configured to generate a first comparison voltage anda second comparison voltage having a level higher than that of the firstcomparison voltage by dividing the power voltage; a first comparatorconfigured to output a low voltage detection enable signal by comparingthe first comparison voltage with a reference voltage; a secondcomparator configured to output a detection signal by comparing thesecond comparison voltage with the reference voltage while the lowvoltage detection enable signal is being input; a detection signalmaintainer configured to provide a low voltage detection signal to anoutput terminal according to the detection signal; and an output signaldischarger configured to discharge the low voltage detection signalaccording to the low voltage detection enable signal.

According to another aspect of the present disclosure, there is provideda memory device including: a memory cell array; a low voltage detectorconfigured to generate, while a first comparison voltage is lower than areference voltage, a detection signal when a second comparison voltagebecomes lower than the reference voltage or when the second comparisonvoltage then becomes higher than the reference voltage; and controllogic configured to discharge an operation voltage to the memory cellarray according to the detection signal, wherein the first and secondcomparison voltages are divided from a power voltage, and wherein thefirst comparison voltage is lower than the second comparison voltage.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments will now be described more fully with reference tothe accompanying drawings; however, elements and features of theembodiments may be configured or arranged differently than illustratedand described. Thus, the present invention is not limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure is thorough and complete and fully conveys thescope of the embodiments to those skilled in the art.

In the drawing figures, dimensions may be exaggerated for clarity ofillustration. It will be understood that when an element is referred toas being “between” two elements, it can be the only element between thetwo elements, or one or more intervening elements may also be present.Like reference numerals refer to like elements throughout.

FIG. 1 is a diagram illustrating a storage device according to anembodiment of the present disclosure.

FIG. 2 is a circuit diagram of a conventional low voltage detectioncircuit.

FIG. 3 is a waveform diagram illustrating an operation of the lowvoltage detection circuit of FIG. 2.

FIG. 4 is a circuit diagram illustrating a low voltage detection circuitaccording to an embodiment of the present disclosure.

FIG. 5 is a waveform diagram illustrating an operation of the lowvoltage detection circuit of FIG. 4.

FIG. 6 is a circuit diagram illustrating a low voltage detection circuitaccording to another embodiment of the present disclosure.

FIG. 7 is a diagram illustrating a structure of a memory device of FIG.1.

FIG. 8 is a diagram illustrating an embodiment of a memory cell array ofFIG. 7.

FIG. 9 is a circuit diagram illustrating any one memory block amongmemory blocks of FIG. 8.

FIG. 10 is a circuit diagram illustrating another embodiment of the onememory block among the memory blocks of FIG. 8.

FIG. 11 is a block diagram illustrating a memory system including thememory device of FIG. 7.

FIG. 12 is a block diagram illustrating an exemplary application of thememory system of FIG. 11.

FIG. 13 is a block diagram illustrating a computing system including thememory system described with reference to FIG. 12.

DETAILED DESCRIPTION

The specific structural and functional description herein is merely forthe purpose of describing embodiments of the present disclosure. Theembodiments can be implemented in various other ways, and thus thepresent invention is not limited to the embodiments set forth herein.

Various aspects (e.g., shape, configuration, and the like) of elementsand features of the disclosed embodiments may be modified in variousways. Thus, embodiments of the present disclosure are not to beconstrued as limited to specified disclosures, but rather include allchanges, equivalents, or substitutes that do not depart from the spiritand technical scope of the present disclosure.

While terms such as “first” and “second” may be used to identify variouscomponents, such components are not limited to the above terms. Theabove terms are used only to distinguish one component from another thatotherwise have the same or similar names. For example, a first componentmay be referred to as a second component without departing from thescope of the present disclosure, and likewise a second component may bereferred to as a first component.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements mayalso be present. In contrast, when an element is referred to as being“directly connected” or “directly coupled” to another element, nointervening elements are present. Other expressions describingrelationships between components such as “between,” “immediatelybetween” or “adjacent to” and “directly adjacent to” are to be construedsimilarly.

The terms used in the present application are merely used to describeparticular embodiments, and are not intended to limit the presentdisclosure. Singular forms in the present disclosure are intended toinclude the plural forms and vice versa, unless the context clearlyindicates otherwise. It will be further understood that terms such as“including” or “having,” etc., are intended to indicate the presence ofstated features, numbers, operations, actions, components, parts, orcombinations thereof, but are not intended to preclude the presence oraddition of one or more other features, numbers, operations, actions,components, parts, or combinations thereof.

Unless defined differently, all terms used herein including technical orscientific terminologies have meanings that are commonly understood bythose skilled in the art to which the present disclosure pertains.Ordinary, dictionary-defined terms should be construed consistent withthe context of the related technique. Unless dearly defined in thisapplication, terms should not be understood or construed in an ideallyor excessively formal way.

Description of techniques that are well known to the art to which thepresent disclosure pertains and not directly related to the presentdisclosure is omitted so as not to unnecessarily obscure aspects andfeatures of the present invention.

Various embodiments of the present disclosure will be described indetail with reference to the accompanying drawings in order for thoseskilled in the art to be able to readily implement the presentinvention. It is noted that, throughout the specification, reference to“an embodiment” or the like is not necessarily to only one embodiment,and different references to “an embodiment” or the like are notnecessarily to the same embodiment(s).

FIG. 1 is a diagram illustrating a storage device according to anembodiment of the present disclosure.

Referring to FIG. 1, the storage device may include a memory device 100,a memory controller 200, and a power management integrated circuit(PMIC) 300.

The storage device 50 may store data under the control of a host 400,such as a mobile phone, a smart phone, an MP3 player, a laptop computer,a desktop computer, a game console, a TV, a tablet PC or an in-vehicleinfotainment system.

The storage device 50 may be any one of various types of storage devicesaccording to a host interface protocol for communication with the host400. For example, the storage device 50 may be implemented with any oneof various types of storage devices such as a multi-media card of asolid state drive (SSD), a multi-media card (MMC), an embedded,multi-media card (eMMC), a reduced size, multi-media card (RS-MMC), anda micro-multi-media card (micro-MMC) type, a secure digital (SD) card ofa secure digital (SD), a mini-secure digital (mini-SD) and amicro-secure digital (micro-SD) type, an universal storage bus (USB)storage device, a universal flash storage (UFS) device, a storage deviceof a personal computer memory card international association (PCMCIA)card type, a storage device of a peripheral component interconnection(PCI) card type, a storage device of a PCI-express (PCI-E) card type, acompact flash (CF) card, a smart media card, and a memory stick.

The storage device 50 may be manufactured as any one of various kinds ofpackage types such as a package-on-package (POP), a system-in-package(SIP), a system-on-chip (SOC), a multi-chip package (MCP), achip-on-board (COB), a wafer-level fabricated package (WFP), and awafer-level stack package (WSP).

The memory device 100 may store data. The memory device 100 operatesunder the control of the memory controller 200. The memory device 100may include a memory cell array (not shown) including a plurality ofmemory cells for storing data. In an embodiment, the memory device 100may be a Double Data Rate Synchronous Dynamic Random Access Memory (DDRSDRAM), a Low Power Double Data Rate 4 (LPDDR4) SDRAM, a Graphics DoubleData Rate (GDDR) SRAM, a Low Power DDR (LPDDR), a Rambus Dynamic RandomAccess Memory (RDRAM), a NAND flash memory, a vertical NAND flashmemory, a NOR flash memory, a Resistive Random Access Memory (RRAM), aPhase-Change Random Access Memory (PRAM), a Magnetoresistive RandomAccess Memory (MRAM), a Ferroelectric Random Access Memory (FRAM), aSpin Transfer Torque Random Access Memory (STT-RAM), or the like.

The memory device 100 is configured to receive a command and an addressfrom the memory controller 200 and access an area selected by theaddress in the memory cell array. That is, the memory device 100 mayperform an operation corresponding to the command on the area selectedby the address. For example, the memory device 100 may perform a programoperation, a read operation, and an erase operation. In the programoperation, the memory device 100 may program data in the area selectedby the address. In the read operation, the memory device 100 may readdata from the area selected by the address. In the erase operation, thememory device 100 may erase data stored in the area selected by theaddress.

In an embodiment, the program operation and the read operation may beperformed in units of pages, and the erase operation may be performed inunits of blocks.

The memory device 100 may receive a power voltage VCCE from the PMIC300. In order to ensure the reliability of the memory device 100, thememory device 100 may perform various management operations according tochanges in level of the power voltage VCCE.

For example, when a sudden power off (SPO) occurs due to sudden cut offof the supply of a power voltage from the PMIC 300, a defect may occur,such as loss of data being programmed in the memory device 100.Therefore, the memory device 100 may monitor the level of the powervoltage VCCE so as to safely preserve data in the event of a suddenpower-off.

When the sudden power-off is predicted from the power voltage VCCE beinglowered to a certain level or less, the memory device 100 may perform anoperation of discharging voltages supplied to a word line WL and a bitline BL coupled to memory cells included in the memory device 100. Astate in which the power voltage VCCE is at a certain low level or lessmay be defined as a low voltage state. The memory device 100 may furtherinclude a low voltage detection circuit 140 for detecting the lowvoltage state.

In an embodiment, the low voltage detection circuit 140 may compare thepower voltage VCCE with a preset reference voltage V_(REF) and outputs adetection signal when the level of the power voltage VCCE is lower thanthe reference voltage V_(REF). In another embodiment, the low voltagedetection circuit 140 does not compare the power voltage VCCE with thereference voltage V_(REF), but may generate a comparison voltage V_(DIV)compared with the reference voltage V_(REF), based on the power voltageVCCE. In that case, the low voltage detection circuit 140 may comparethe comparison voltage V_(DIV) with the reference voltage V_(REF) andoutput a low voltage detection signal when the comparison voltageV_(DIV) is lower than the reference voltage V_(REF).

In an embodiment, the memory device 100 may include a power on reset(POR) circuit to prevent malfunction when the power voltage VCCEsupplied. When the power voltage VCCE is applied to the memory device100 and then reaches a set or predetermined level, the POR circuit mayprovide a reset signal for initializing a flip-flop, a latch, a counter,a register, and the like, which constitute the memory device 100. Forexample, the memory device 100 outputs an activated reset signal whenthe power voltage VCCE reaches a set or predetermined level in power on.Subsequently, when the power voltage VCCE reaches a normal operationvoltage, the reset signal is inactivated. Internal components of thememory device 100 may be reset to an initial state in response to theactivated reset signal. In an embodiment, the POR circuit and the lowvoltage detection circuit 140 are separate circuits, and may detect thelevel of the power voltage VCCE.

The memory controller 1200 may control the overall operations of thememory device 1100. The memory controller 200 may control an operationof the memory device 100 in response to a request from the host 400 orregardless of the request from the host 400.

For example, the memory controller 200 may control the memory device 100to perform a program operation, a read operation, an erase operation, orthe like in response to a request from the host 400. In the programoperation, the memory controller 200 may provide a program command, anaddress, and data to the memory device 100. In the read operation, thememory controller 200 may provide a read command and an address to thememory device 100. In the erase operation, the memory controller 200 mayprovide an erase command and an address to the memory device 100.

In an embodiment, the memory controller 200 may autonomously generate aprogram command, an address, and data without any request from the host400, and transmit the program command, the address, and the data to thememory device 100. For example, the memory controller 200 may providethe command, the address, and the data to the memory device 100 toperform background operations such as a program operation for wearleveling and a program operation for garbage collection.

The memory controller 200 may execute firmware (FW) for controlling thememory device 100. When the memory device 100 is a flash memory device,the memory controller 200 may be configured to operate firmware such asa Flash Translation Layer (FTL) for controlling communication betweenthe host 400 and the memory device 100. Specifically, the memorycontroller 200 may translate a logical address included in a requestfrom the host 400 into a physical address that is to be provided to thememory device 100.

The PMIC 300 may provide power voltages required to operate the memorydevice 100 and the memory controller 200. In an embodiment, the voltagesprovided by the PMIC 300 may be 3.3V and 1.8V.

The host 400 may communicate with the storage device 50, using at leastone of various communication protocols, such as a Universal Serial bus(USB), a Serial AT Attachment (SATA), a High Speed InterChip (HSIC), aSmall Computer System Interface (SCSI), Firewire, a Peripheral ComponentInterconnection (PCI), a PCI express (PCIe), a nonvolatile memoryexpress (NVMe), a universal flash storage (UFS), a Secure Digital (SD),a Multi-Media Card (MMC), an embedded MMC (eMMC), a Dual In-line MemoryModule (DIMM), a Registered DIMM (RDIMM), and a Load Reduced DIMM(LRDIMM).

FIG. 2 is a circuit diagram of a conventional low voltage detectioncircuit.

Referring to FIG. 2, the low voltage detection circuit 20 may include avoltage input 21, a comparison voltage generator 22, and a voltagecomparator 23.

The voltage input 21 may be coupled in series to a power voltageterminal T20 and the comparison voltage generator 22. The voltage input21 may provide a power voltage VCCE input through the power voltageterminal T20 to the comparison voltage generator 22 in response to anenable signal EN input from an input signal terminal T21. In anembodiment, the voltage input 21 may include a P-type transistor. Theenable signal EN may be provided to a gate of the P-type transistor.

The comparison voltage generator 22 may be coupled in series between thevoltage input 21 and a ground voltage GND. The comparison voltagegenerator 22 may generate a comparison voltage V_(DIV) obtained bydividing the power voltage VCCE input from the voltage input 21. Thecomparison voltage generator 22 may output the generated comparisonvoltage V_(DIV) to the voltage comparator 23. In an embodiment, thecomparison voltage generator 22 may include a plurality of resistors R.The comparison voltage generator 22 may output, as the comparisonvoltage V_(DIV), a voltage of a selected node among the plurality ofresistors R.

The voltage comparator 23 may include an operational amplifier (OP AMP).The voltage comparator 23 may receive the comparison voltage V_(DIV)output from the comparison voltage generator 22 through an invertingterminal, and receive a reference voltage V_(REF) through anon-inverting terminal.

When the voltage level of the comparison voltage V_(DIV) is lower thanthe reference voltage V_(REF), the voltage comparator 23 may output alow voltage detection signal LVCC DETECT through an output terminal T22.

When the storage device 50 described with reference to FIG. 1 is amobile device such as a mobile phone or a tablet PC, the supplyperformance of the PMIC 300 may be decreased when the power of a batteryof the mobile device is decreased. There may occur a situation in whichthe power voltage VCCE applied to the memory device 100 decreases to alow voltage state and then returns to the original state. Also, theremay occur a situation in which, when the power voltage VCCE is in thelow voltage state, the reference voltage V_(REF) input to the lowvoltage detection circuit 20 also drops or is low. When the decreasedreference voltage VREF is less than the comparison voltage V_(DIV), thelow voltage detection signal LVCC DETECT is no longer output since thereference voltage V_(REF) is lower than the comparison voltage V_(DIV)even though the power voltage VCCE is in a state in which it has alreadybeen lowered to the low voltage state. Therefore, malfunction may becaused in the memory device 100.

FIG. 3 is a waveform diagram illustrating an operation of the lowvoltage detection circuit 20 of FIG. 2.

Referring to FIGS. 2 and 3, the level of the power voltage VCCEmaintains a normal level before t0.

The voltage level of the power voltage VCCE decreases at t0. Decrease ofthe voltage level of the power voltage VCCE may occur due to variouscauses. Since the comparison voltage V_(DIV) is obtained by dividing thepower voltage VCCE, the comparison voltage V_(DIV) may decrease when thepower voltage VCCE decreases. However, the timing and slope where thecomparison voltage V_(DIV) decreases may be different from those wherethe power voltage VCCE decreases due to various factors.

The level of the comparison voltage V_(DIV) starts to become lower thanthe reference voltage V_(REF) at time t1, and hence the input powervoltage VCCE corresponds to the low voltage state. Therefore, the lowvoltage detection circuit 20 may output the low voltage detection signalLVCC DETECT.

There may occur a situation in which, when the power voltage VCCE is inthe low voltage state, the reference voltage V_(REF) input to the lowvoltage detection circuit 20 is also lower.

The level of the reference voltage V_(REF) also decreases between timest1 and t2.

When the level of the reference voltage V_(REF) decreases to a voltagelevel lower than that of the comparison voltage V_(DIV) starting at timet2, the voltage comparator 23 of the low voltage detection circuit 20may not output the low voltage detection signal LVCC DETECT.

The level of the reference voltage V_(REF) may start again increasingjust before time t3 and between times t3 and t4.

The level of the reference voltage V_(REF) starts to have a voltagelevel higher than that of the comparison voltage V_(DIV) at time t3, andhence the low voltage detection signal LVCC DETECT may be again output.

The level of the comparison voltage V_(DIV) may start again increasingbetween times t3 and t4.

The level of the comparison voltage V_(DIV) starts to have a voltagelevel higher than that of the reference voltage V_(REF) at time t4, andhence the input power voltage VCCE is no longer the low voltage state.Therefore, the low voltage detection signal LVCC DETECT is not output.

At time t5, the level of the power voltage VCCE is restored to the statebefore time t0.

In FIG. 3, the time period in which the power voltage VCCE is actuallyin the low voltage state is from time t1 to time t4. In the low voltagedetection circuit 20 described with reference to FIG. 2, when thedecreased reference voltage V_(REF) is lower than the comparison voltageV_(DIV), the low voltage detection signal LVCC DETECT is no longeroutput since the reference voltage V_(REF) is lower than the comparisonvoltage V_(DIV) even though the power voltage VCCE has already beenlowered to the low voltage state. Therefore, there may occur a problemin that, although the power voltage VCCE is actually in the low voltagestate, the low voltage detection signal LVCC DETECT is not output.

FIG. 4 is a circuit diagram illustrating a low voltage detection circuit140 according to an embodiment of the present disclosure.

Referring to FIG. 4, the low voltage detection circuit 140 may include avoltage provider 141, a comparison voltage generator 142, a firstcomparator 143, a second comparator 144, a detection signal maintainer145, and an output signal discharger 146.

The voltage provider 141 may be coupled in series to a power voltageterminal T1 and the comparison voltage generator 142. The voltageprovider 141 may provide a power voltage VCCE input through the powervoltage terminal T1 to the comparison voltage generator 142 in responseto an operation enable signal ENABLE_N input from an input signalterminal T2. In an embodiment, the voltage provider 141 may include afirst P-type transistor P1. The operation enable signal ENABLE_N may beprovided to a gate of the first P-type transistor P1.

The comparison voltage generator 142 may be coupled in series betweenthe voltage provider 141 and a ground voltage GND. The comparisonvoltage generator 142 may generate a first comparison voltageV_(DIV_ENABLE) and a second comparison voltage V_(DIV) by dividing thepower voltage VCCE input from the voltage provider 141. The comparisonvoltage generator 142 may provide the generated first comparison voltageV_(DIV_ENABLE) to the first comparator 143, and provide the generatedsecond comparison voltage V_(DIV) to the second comparator 144. In anembodiment, the level of the first comparison voltage V_(DIV_ENABLE) maybe lower than that of the second comparison voltage V_(DIV).

In an embodiment, the comparison voltage generator 142 may include aplurality of resistors R. The comparison voltage generator 142 mayoutput the power voltage VCCE as the first comparison voltageV_(DIV_ENABLE) or the second comparison voltage V_(DIV).

The first comparator 143 may include an operational amplifier (OP AMP).The first comparator 143 may receive the first comparison voltageV_(DIV_ENABLE) output from the comparison voltage generator 142 throughan inverting terminal, and receive a reference voltage V_(REF) through anon-inverting terminal.

The first comparator 143 may compare levels of the first comparisonvoltage V_(DIV_ENABLE) and the reference voltage V_(REF). The firstcomparator 143 may output, to a first node Node1, a result obtained bycomparing the levels of the first comparison voltage V_(DIV_ENABLE) andthe reference voltage V_(REF). Specifically, when the level of the firstcomparison voltage V_(DIV_ENABLE) is lower than that of the referencevoltage V_(REF), the first comparator 143 may output a low voltagedetection enable signal LVCC_DETECT_ENABLE. When the level of the firstcomparison voltage V_(DIV_ENABLE) is greater than or equal to that ofthe reference voltage V_(REF), the first comparator 143 may not outputthe low voltage detection enable signal LVCC_DETECT_ENABLE.

In an embodiment, when the level of the first comparison voltageV_(DIV_ENABLE) is lower than that of the reference voltage V_(REF), thefirst comparator 143 may output the low voltage detection enable signalLVCC_DETECT_ENABLE having a logic high level. Alternatively, when thelevel of the first comparison voltage V_(DIV_ENABLE) is greater than orequal to that of the reference voltage V_(REF), the first comparator 143may output the low voltage detection enable signal LVCC_DETECT_ENABLEhaving a logic low level.

The second comparator 144 may include an operational amplifier (OP AMP).The second comparator 144 may receive a second comparison voltageV_(DIV) output from the comparison voltage generator 142 through aninverting terminal, and receive the reference voltage V_(REF) through anon-inverting terminal. The second comparator 144 may compare the secondcomparison voltage V_(DIV) and the reference voltage V_(REF). When thesecond comparison voltage V_(DIV) is lower than the reference voltageV_(REF), the second comparator 144 may output a detection signal DETECTto a second node Node2.

In an embodiment, the second comparator 144 may operate in response tothe low voltage detection enable signal LVCC_DETECT_ENABLE output fromthe first comparator 143 as an enable signal. For example, the secondcomparator 144 may output a result obtained by comparing the secondcomparison voltage V_(DIV) and the reference voltage V_(REF) only whilethe low voltage detection enable signal LVCC_DETECT_ENABLE output fromthe first comparator 143 is being input.

Specifically, while the low voltage detection enable signalLVCC_DETECT_ENABLE output from the first comparator 143 is being input,the second comparator 144 may output the detection signal DETECT whenthe second comparison voltage V_(DIV) is lower than the referencevoltage V_(REF), and may not output the detection signal DETECT when thesecond comparison voltage V_(DIV) is greater than or equal to thereference voltage V_(REF). In an embodiment, when the low voltagedetection enable signal LVCC_DETECT_ENABLE is not input, the secondcomparator 144 may not output any signal.

The detection signal maintainer 145 may be coupled between the secondnode Node2 and an output terminal T3. The detection signal maintainer145 may output a low voltage detection signal LVCC DETECT to the outputterminal T3 in response to the detection signal DETECT of the secondnode Node2. The detection signal maintainer 145 may maintain the lowvoltage detection signal LVCC DETECT output to the output terminal T3.Specifically, the detection signal maintainer 145 may include a firstN-type transistor N1, a first inverter IV1, and a second inverter IV2.The first N-type transistor N1 may be coupled between the second nodeNode2 and a third node Node3. A gate of the first N-type transistor N1is coupled to the second node Node2. A source of the first N-typetransistor N1 is coupled to the ground voltage GND. A drain of the firstN-type transistor N1 may be coupled to the third node Node3. The firstinverter IV1 and the second inverter IV2 may be coupled in parallel toconstitute one latch. One end of the latch may be coupled to the thirdnode Node3, and the other end of the latch may be coupled to the outputterminal T3.

The third node Node3 may have, as an initial value, a voltage of thelogic high level. When the second comparator 144 outputs the detectionsignal DETECT to the second node Node2, the first N-type transistor N1is turned on, and the third node Node3 may be discharged. The lowvoltage detection signal LVCC DETECT may be output to the outputterminal T3 by the first inverter IV1 and the second inverter IV2. Evenwhen the second comparator 144 does not output the detection signalDETECT any more, the third node Node3 is maintained to have the voltageof the logic low level by the first inverter IV1 and the second inverterIV2, and the low voltage detection signal LVCC DETECT of the outputterminal T3 may be maintained.

The output signal discharger 146 may discharge the low voltage signalLVCC DETECT being output to the output terminal T3. The output signaldischarger 146 may be coupled between the first node Node1 and theoutput terminal T3. The output signal discharger 146 may receive the lowvoltage detection enable signal LVCC_DETECT_ENABLE output to the firstnode Node1 by the first comparator 143. The output signal discharger 146may discharge the output node T3 in response to the low voltagedetection enable signal LVCC_DETECT_ENABLE.

The output signal discharger 146 may include a third inverter IV3 and asecond N-type transistor N2. One end of the third inverter IV3 may becoupled to the first node Node1, and the other end of the third inverterIV3 may be coupled to a fourth node Node4. A gate of the second N-typetransistor N2 may be coupled to the fourth node Node4. A source of thesecond N-type transistor N2 may be coupled to the ground voltage GND. Adrain of the second N-type transistor N2 may be coupled to the outputterminal T3.

When the first comparison voltage V_(DIV_ENABLE) is lower than thereference voltage V_(REF), the first comparator 143 may output the lowvoltage detection enable signal LVCC_DETECT_ENABLE to the first nodeNode1.

The third inverter IV3 inverts the low voltage detection enable signalLVCC_DETECT_ENABLE and transfers the inverted low voltage detectionenable signal LVCC_DETECT_ENABLE to the fourth node Node4. When the lowvoltage detection enable signal LVCC_DETECT_ENABLE is in the logic highlevel, the fourth node Node4 may be in the logic low level. On thecontrary, when the low voltage detection enable signalLVCC_DETECT_ENABLE is in the logic low level, the fourth node Node4 maybe in the logic high level. The second N-type transistor N2 may beturned on when the fourth node Node4 is in the logic high level, and beturned off when the fourth node Node4 is in the logic low level.Therefore, when the low voltage detection enable signalLVCC_DETECT_ENABLE is in the logic low level, the output signaldischarger 146 may discharge the low voltage detection signal LVCCDETECT being output to the output terminal T3.

FIG. 5 is a waveform diagram illustrating an operation of the lowvoltage detection circuit 140 of FIG. 4.

Referring to FIGS. 4 and 5, the level of the power voltage VCCEmaintains a normal level before time T0.

The voltage level of the power voltage VCCE decreases starting at timeT0. Decrease of the voltage level of the power voltage VCCE may occurdue to various causes. Since the first comparison voltage V_(DIV_ENABLE)is a voltage obtained by dividing the power voltage VCCE, the firstcomparison voltage V_(DIV_ENABLE) may also decrease when the powervoltage VCCE decreases. However, the timing and slope where the firstcomparison voltage V_(DIV_ENABLE) and the second comparison voltageV_(DIV) decrease may be different from those where the power voltageVCCE decreases due to various factors.

At time T1, the level of the second comparison voltage V_(DIV) is higherthan the reference voltage V_(REF), but the voltage of the firstcomparison voltage V_(DIV_ENABLE) starts to become lower than thereference voltage V_(REF). Therefore, the low voltage detection enablesignal LVCC_DETECT_ENABLE may be output.

At time T2, the first comparison voltage V_(DIV_ENABLE) may be in astate in which it is still lower than the reference voltage V_(REF), andthe second comparison voltage V_(DIV) may also start to become lowerthan the reference voltage V_(REF). Therefore, the second comparator 144may output the detection signal DETECT, and the output terminal T3 mayoutput the low detection signal LVCC DETECT. There may occur a situationin which, when the power voltage VCCE is in the low voltage state, thereference voltage V_(REF), which is input to the low voltage detectioncircuit 140, may also decrease.

The level of the reference voltage V_(REF) also decreases between thetime points T2 and T3.

When the level of the reference voltage V_(REF) decreases to a voltagelower than the second comparison voltage V_(DIV) starting at time T3,the second comparator 144 of the low voltage detection circuit 140 maynot output the detection signal DETECT. However, the voltage comparator23 may not output the low voltage detection signal LVCC DETECT. However,the low voltage detection signal LVCC DETECT may be maintained due tothe latch included in the detection signal maintainer 145.

The level of the reference voltage V_(REF) may start again increasingbetween time points T3 and T4.

The voltage level of the reference voltage V_(REF) starts to becomehigher than that of the second comparison voltage V_(DIV) at time T4,and hence the low voltage detection signal LVCC DETECT may be againoutput.

The levels of the first comparison voltage V_(DIV_ENABLE) and the secondcomparison voltage V_(DIV) may start again increasing between timepoints T4 and T5.

The level of the second comparison voltage V_(DIV) starts to becomehigher than that of the reference voltage V_(REF) at time T5, and hencethe input power voltage VCCE is no longer the low voltage state. Thesecond comparator 144 may not output the detection signal DETECT.

At time T6, the first comparison voltage V_(DIV_ENABLE) starts to have alevel higher than that of the reference voltage V_(REF). Therefore, thefirst comparator 143 does not output the low voltage detection enablesignal LVCC_DETECT_ENABLE. When the low voltage detection enable signalLVCC_DETECT_ENABLE is changed to have the logic low level, the outputsignal discharger 146 may discharge the low detection signal LVCC DETECTof the output terminal T3.

At time T6, the level of power voltage VCCE returns to the state orlevel that it had before time T0.

In FIG. 5, the time period in which the power voltage VCCE is in the lowvoltage state is from time T2 to time T5. In the low voltage detectioncircuit 140 described with reference to FIG. 4, although the decreasedreference voltage V_(REF) is less than the second comparison voltageV_(DIV), the low voltage detection signal LVCC DETECT of the outputterminal at time T3 is maintained to have the logic high level. Thus,the problem can be prevented, in that although the power voltage VCCE isactually in the low voltage state, the low voltage detection signal LVCCDETECT is not output.

In the embodiment described with reference to FIGS. 4 and 5, each of thefirst comparison voltage V_(DIV_ENABLE) and the second comparisonvoltage V_(DIV) is compared with the reference voltage V_(REF). However,the present disclosure is not limited to this embodiment.

In an embodiment, each of the first comparison voltage V_(DIV_ENABLE)and the second comparison voltage V_(DIV) may be compared with referencevoltages having different levels. For example, the first comparator 143described with reference to FIG. 4 may compare the first comparisonvoltage V_(DIV_ENABLE) with a first reference voltage V_(REF1) (notshown), and the second comparator 144 described with reference to FIG. 4may compare the second comparison voltage V_(DIV) with a secondreference voltage V_(REF2) (not shown). The first reference voltageV_(REF1) may be a voltage higher than the second reference voltageV_(REF2). In this case, discharge of the low voltage detection signalLVCC DETECT may be further delayed as compared with that in theembodiment of FIG. 4. Accordingly, there can be sufficient time requiredfor the power voltage VCCE to be restored to the normal level.

FIG. 6 is a circuit diagram illustrating a low voltage detection circuit140-2 according to another embodiment of the present disclosure.

Referring to FIG. 6, the low voltage detection circuit 140-2 may includea voltage provider 141′, a comparison voltage generator 142′, a firstcomparator 143′, a second comparator 144′, a detection signal maintainer145′, and an output signal discharger 146′.

The voltage provider 141′ may be coupled in series to a power voltageterminal T1′ and the comparison voltage generator 142′. The voltageprovider 141′ may provide a power voltage VCCE input through the powervoltage terminal T1′ to the comparison voltage generator 142′ inresponse to an operation enable signal ENABLE_N input from an inputsignal terminal T2′. In an embodiment, the voltage provider 141′ mayinclude a first P-type transistor P1′. The operation enable signalENABLE_N may be provided to a gate of the first P-type transistor P1′.

The comparison voltage generator 142′ may be coupled in series betweenthe voltage provider 141′ and a ground voltage CND. The comparisonvoltage generator 142′ may generate a first comparison voltageV_(DIV_ENABLE) and a second comparison voltage V_(DIV) by dividing thepower voltage VCCE input from the voltage provider 141′. The comparisonvoltage generator 142′ may provide the generated first comparisonvoltage V_(DIV_ENABLE) to the first comparator 143′, and provide thegenerated second comparison voltage V_(DIV) to the second comparator144′. In an embodiment, the level of the first comparison voltageV_(DIV_ENABLE) may be lower than that of the second comparison voltageV_(DIV).

In an embodiment, the comparison voltage generator 142′ may include aplurality of resistors R. The comparison voltage generator 142′ mayoutput the power voltage VCCE as the first comparison voltageV_(DIV_ENABLE) or the second comparison voltage V_(DIV).

The first comparator 143′ may include an operational amplifier (OP AMP).The first comparator 143′ may receive the first comparison voltageV_(DIV_ENABLE) output from the comparison voltage generator 142′ throughan inverting terminal, and receive a reference voltage V_(REF) through anon-inverting terminal.

The first comparator 143′ may compare levels of the first comparisonvoltage V_(DIV_ENABLE) and the reference voltage V_(REF). The firstcomparator 143′ may output, to a first node Node1′, a result obtained bycomparing the levels of the first comparison voltage V_(DIV_ENABLE) andthe reference voltage V_(REF). Specifically, when the level of the firstcomparison voltage V_(DIV_ENABLE) is lower than that of the referencevoltage V_(REF), the first comparator 143′ may output a low voltagedetection enable signal LVCC_DETECT_ENABLE. When the level of the firstcomparison voltage V_(DIV_ENABLE) is greater than or equal to that ofthe reference voltage V_(REF), the first comparator 143′ may not outputthe low voltage detection enable signal LVCC_DETECT_ENABLE.

In an embodiment, when the level of the first comparison voltageV_(DIV_ENABLE) is lower than that of the reference voltage V_(REF), thefirst comparator 143′ may output the low voltage detection enable signalLVCC_DETECT_ENABLE having a logic high level. Alternatively, when thelevel of the first comparison voltage V_(DIV_ENABLE) is greater than orequal to that of the reference voltage V_(REF), the first comparator143′ may output the low voltage detection enable signalLVCC_DETECT_ENABLE having a logic low level.

The second comparator 144′ may include an operational amplifier (OPAMP). The second comparator 144′ may receive a second comparison voltageV_(DIV) output from the comparison voltage generator 142′ through aninverting terminal, and receive the reference voltage V_(REF) through anon-inverting terminal. The second comparator 144′ may compare thesecond comparison voltage V_(DIV) and the reference voltage V_(REF).When the second comparison voltage V_(DIV) is lower than the referencevoltage V_(REF), the second comparator 144 may output a detection signalDETECT to a second node Node2′,

In an embodiment, a delay circuit 147′ may be coupled between the firstnode Node1′ and the second comparator 144′. The delay circuit 147′ maydelay the low voltage detection enable signal LVCC_DETECT_ENABLE of thefirst node Node1′ and provide the delayed low voltage detection enablesignal LVCC_DETECT_ENABLE to the second comparator 144′.

In an embodiment, the second comparator 144 may operate in response tothe low voltage detection enable signal LVCC_DETECT_ENABLE outputthrough the delay circuit 147′ as an enable signal. For example, thesecond comparator 144 may output a result obtained by comparing thesecond comparison voltage V_(DIV) and the reference voltage V_(REF) onlywhile the low voltage detection enable signal LVCC_DETECT_ENABLE outputthrough the delay circuit 147′ is being input.

Specifically, while the low voltage detection enable signalLVCC_DETECT_ENABLE output from the first comparator 143′ is being input,the second comparator 144′ may output the detection signal DETECT whenthe second comparison voltage V_(DIV) is lower than the referencevoltage V_(REF), and may not output the detection signal DETECT when thesecond comparison voltage V_(DIV) is greater than or equal to thereference voltage V_(REF). In an embodiment, when the low voltagedetection enable signal LVCC_DETECT_ENABLE is not input, the secondcomparator 144′ may not output any signal.

The detection signal maintainer 145′ may be coupled between the secondnode Node2′ and an output terminal T3′. The detection signal maintainer145′ may output a low voltage detection signal LVCC DETECT to the outputterminal T3′ in response to the detection signal DETECT of the secondnode Node2′. The detection signal maintainer 145′ may maintain the lowvoltage detection signal LVCC DETECT output to the output terminal T3′.Specifically, the detection signal maintainer 145′ may include a firstN-type transistor N1′, a first inverter IV1′, and a second inverterIV2′. The first N-type transistor N1′ may be coupled between the secondnode Node2′ and a third node Node3′. A gate of the first N-typetransistor N1′ is coupled to the second node Node2′. A source of thefirst N-type transistor N1′ is coupled to the ground voltage GND. Adrain of the first N-type transistor N1′ may be coupled to the thirdnode Node3′. The first inverter IV1′ and the second inverter IV2′ may becoupled in parallel to constitute one latch. One end of the latch may becoupled to the third node Node3′, and the other end of the latch may becoupled to the output terminal T3′.

The third node Node3′ may have, as an initial value, a voltage of thelogic high level. When the second comparator 144′ outputs the detectionsignal DETECT to the second node Node2′, the first N-type transistor N1′is turned on, and the third node Node3′ may be discharged. The lowvoltage detection signal LVCC DETECT may be output to the outputterminal T3′ by the first inverter IV1′ and the second inverter IV2′.Even when the second comparator 144′ does not output the detectionsignal DETECT any more, the third node Node3′ is maintained to have thevoltage of the logic low level by the first inverter IV1′ and the secondinverter IV2′, and the low voltage detection signal LVCC DETECT of theoutput terminal T3′ may be maintained.

The output signal discharger 146′ may discharge the low voltage signalLVCC DETECT being output to the output terminal T3′. The output signaldischarger 146′ may be coupled between the first node Node1′ and theoutput terminal T3′. The output signal discharger 146′ may receive thelow voltage detection enable signal LVCC_DETECT_ENABLE output to thefirst node Node1′ by the first comparator 143′. The output signaldischarger 146′ may discharge the output node T3′ in response to the lowvoltage detection enable signal LVCC_DETECT_ENABLE.

The output signal discharger 146′ may include a third inverter IV3′ anda second N-type transistor N2′. One end of the third inverter IV3′ maybe coupled to the first node Node1′, and the other end of the thirdinverter IV3′ may be coupled to a fourth node Node4′. A gate of thesecond N-type transistor N2′ may be coupled to the fourth node Node4′. Asource of the second N-type transistor N2′ may be coupled to the groundvoltage GND. A drain of the second N-type transistor N2′ may be coupledto the output terminal T3′.

When the first comparison voltage V_(DIV_ENABLE) is lower than thereference voltage V_(REF), the first comparator 143′ may output the lowvoltage detection enable signal LVCC_DETECT_ENABLE to the first nodeNode1′.

The third inverter IV3′ inverts the low voltage detection enable signalLVCC_DETECT_ENABLE and transfers the inverted low voltage detectionenable signal LVCC_DETECT_ENABLE to the fourth node Node4′. When the lowvoltage detection enable signal LVCC_DETECT_ENABLE is in the logic highlevel, the fourth node Node4′ may be in the logic low level. On thecontrary, when the low voltage detection enable signalLVCC_DETECT_ENABLE is in the logic low level, the fourth node Node4′ maybe in the logic high level. The second N-type transistor N2′ may beturned on when the fourth node Node4 is in the logic high level, and beturned off when the fourth node Node4′ is in the logic low level.Therefore, when the low voltage detection enable signalLVCC_DETECT_ENABLE is in the logic low level, the output signaldischarger 146′ may discharge the low voltage detection signal LVCCDETECT being output to the output terminal T3′.

FIG. 7 is a diagram illustrating a structure of the memory device 100 ofFIG. 1.

Referring to FIG. 7, the memory device 100 may include a memory cellarray 110, a peripheral circuit 120, and a control logic 130.

The memory cell array 110 includes a plurality of memory blocks BLK1 toBLKz. The plurality of memory blocks BLK1 to BLKz are coupled to anaddress decoder 121 through row lines RL. The plurality of memory blocksBLK1 to BLKz are coupled to a read/write circuit 123 through bit linesBL1 to BLm. Each of the plurality of memory blocks BLK1 to BLKz includesa plurality of memory cells. In an embodiment, the plurality of memorycells are nonvolatile memory cells. Among the plurality of memory cells,memory cells coupled to the same word line are defined as one page. Thatis, the memory cell array 110 is configured with a plurality of pages.In an embodiment, each of the plurality of memory blocks BLK1 to BLKz inthe memory cell array 110 may include a plurality of dummy cells. One ormore dummy cells may be coupled in series between a drain selecttransistor and memory cells and between a source select transistor andmemory cells.

Each of the memory cells of the memory device 100 may be configured as asingle level cell (SLC) for storing one data bit, a multi-level cell(MLC) for storing two data bits, a triple level cell (TLC) for storingthree data bits, or a quad level cell (QLC) for storing four data bits.

The peripheral circuit 120 may include the address decoder 121, avoltage generator 122, the read/write circuit 123, and a datainput/output circuit 124.

The peripheral circuit 120 drives the memory cell array 110. Forexample, the peripheral circuit 120 may drive the memory cell array 120to perform program, read, and erase operations.

The address decoder 121 is coupled to the memory cell array 110 throughthe row lines RL. The row lines RL may include drain select lines, wordlines, source select lines, and a common source line. In an embodiment,the word lines may include normal word lines and dummy word lines. In anembodiment, the row lines RL may further include a pipe select line.

The address decoder 121 may operate in response to the control of thecontrol logic 130. The address decoder 121 receives an address ADDR fromthe control logic 130.

The address decoder 121 may decode a block address in the receivedaddress ADDR. The address decoder 121 selects at least one memory blockamong the memory blocks BLK1 to BLKz according to the decoded blockaddress. The address decoder 121 may decode a row address in thereceived address ADDR. The address decoder 121 may select at least oneword line WL of the selected memory block by applying voltages providedfrom the voltage generator 122 to the word line WL according to thedecoded row address.

In a program operation, the address decoder 121 may apply a programvoltage to the selected word line, and apply a pass voltage having alevel lower than that of the program voltage to unselected word lines.In a program verify operation, the address decoder 121 may apply averify voltage to the selected word line, and apply a verify passvoltage higher than the verify voltage to the unselected word lines.

In a read operation, the address decoder 121 may apply a read voltage tothe selected word line, and apply a pass voltage higher than the readvoltage to the unselected word lines.

In an embodiment, an erase operation of the memory device 100 isperformed in units of memory blocks. In an erase operation, the addressADDR input to the memory device 100 includes a block address. Theaddress decoder 121 may decode the block address and select one memoryblock according to the decoded block address. In the erase operation,the address decoder 121 may apply a ground voltage to word lines coupledto the selected memory block.

In an embodiment, the address decoder 121 may decode a column address inthe address ADDR transmitted thereto. The decoded column address may betransmitted to the read/write circuit 123. As an example, the addressdecoder 121 may include components such as a row decoder, a columndecoder, and an address buffer.

The voltage generator 122 may generate a plurality of voltages by usingan external power voltage supplied to the memory device 100. The voltagegenerator 122 operates in response to the control of the control logic130.

In an embodiment, the voltage generator 122 may generate an internalpower voltage by regulating the external power voltage. The internalpower voltage generated by the voltage generator 122 is used as anoperation voltage of the memory device 100.

In an embodiment, the voltage generator 122 may generate a plurality ofvoltages by using the external power voltage or the internal powervoltage. The voltage generator 122 may be configured to generate variousvoltages required by the memory device 100. For example, the voltagegenerator 122 may generate a plurality of erase voltages, a plurality ofprogram voltages, a plurality of pass voltages, a plurality of selectread voltages, and a plurality of unselect read voltages.

In order to generate a plurality of voltages having various voltagelevels, the voltage generator 122 may include a plurality of pumpingcapacitors for receiving the internal power voltage, and generate aplurality of voltages by selectively activating the plurality of pumpingcapacitors in response to the control of the control logic 130.

The plurality of generated voltages may be supplied to the memory cellarray 110 by the address decoder 121.

The voltage generator 122 may include a low voltage detection circuit140. The low voltage detection circuit 140 may provide the low voltagedetection signal LVCC DETECT to the control logic 130 when the powervoltage VCCE corresponds to the low voltage state. When the low voltagedetection signal LVCC DETECT is input, the control logic 130 maydischarge a voltage applied to the word lines or bit lines coupled tothe memory cell array 110.

In an embodiment, the low voltage detection circuit 140 of FIG. 7 may beconfigured as described with reference to FIG. 4. In other embodiments,the low voltage detection circuit 140 of FIG. 7 may be the low voltagedetection circuit 140-2 described with reference to FIG. 6.

The read/write circuit 123 includes first to mth page buffers PB1 toPBm. The first to mth page buffers PB1 to PBm are coupled to the memorycell array 110 through the respective first to mth bit lines BL1 to BLm.The first to mth page buffers PB1 to PBm operate in response to thecontrol of the control logic 130.

The first to mth page buffers PB1 to PBm communicate data with the datainput/output circuit 124. In a program operation, the first to mth pagebuffers PB1 to PBm receive data DATA to be stored through the datainput/output circuit 124 and data lines DL.

In a program operation, the first to mth page buffers PB1 to PBm maytransmit, to selected memory cells, the data DATA to be stored, which isreceived through the data input/output circuit 124, when a program pulseis applied to a selected word line. The memory cells of the selectedpage may be programmed according to the transmitted data DATA. A memorycell coupled to a bit line to which a program permission voltage (e.g.,a ground voltage) is applied may have an increased threshold voltage.The threshold voltage of a memory cell coupled to a bit line to which aprogram prohibition voltage (e.g., a power voltage) is applied may bemaintained. In a program verify operation, the first to mth page buffersPB1 to PBm read page data from the selected memory cells through the bitlines BL1 to BLm.

In a read operation, the read/write circuit 123 pray read data DATA frommemory cells of a selected page through the bit lines BL, and store theread data DATA in the first to mth page buffers PB1 to PBm.

In an erase operation, the read/write circuit 123 may allow the bitlines BL to be floated. In an embodiment, the read/write circuit 123 mayinclude a column select circuit.

The data input/output circuit 124 is coupled to the first to mth pagebuffers PB1 to PBm through the data lines DL. The data input/outputcircuit 124 operates in response to the control of the control logic130.

The data input/output circuit 124 may include a plurality ofinput/output buffers (not shown) that receive input data. In a programoperation, the data input/output circuit 124 may receive data DATA to bestored from an external controller (not shown). In a read operation, thedata input/output circuit 124 outputs, to the external controller, datatransmitted from the first to meth page buffers PB1 to PBm included inthe read/write circuit 123.

The control logic 130 may be coupled to the address decoder 121, thevoltage generator 122, the read/write circuit 123, and the datainput/output circuit 124. The control logic 130 may be configured tocontrol overall operations of the memory device 100. The control logic130 may operate in response to a command CMD transmitted from anexternal device.

FIG. 8 is a diagram illustrating an embodiment of the memory cell arrayof FIG. 7.

Referring to FIG. 8, the memory cell array 110 may include a pluralityof memory blocks BLK1 to BLKz. Each memory block may have athree-dimensional structure. Each memory block may include a pluralityof memory cells stacked on a substrate (not shown). The plurality ofmemory cells may be arranged along +X, +Y, and +Z directions. AlthoughFIG. 4 shows memory blocks having the three-dimensional structure, thepresent disclosure is not limited thereto; memory blocks may also beembodied in a two-dimensional structure. A structure of each memoryblock will be described in more detail with reference to FIGS. 9 and 10.

FIG. 9 is a circuit diagram illustrating any one memory block BLKa amongthe memory blocks BLK1 to BLKz of FIG. 8.

Referring to FIG. 9, the memory block BLKa may include a plurality ofcell strings CS11 to CS1 m and CS21 to CS2 m. In an embodiment, each ofthe plurality of cell strings CS11 to CS1 m and CS21 to CS2 m may beformed in a ‘U’ shape. In the memory block BLKa, m cell strings arearranged in a row direction (i.e., a +X direction). Although FIG. 9illustrates two cell strings arranged in a column direction (i.e., a +Ydirection), such illustration is for clarity. The present disclosure isnot limited thereto. Three or more cell strings may be arranged in thecolumn direction.

Each of the plurality of cell strings CS11 to CS1 m and CS21 to CS2 mmay include at least one source select transistor SST, first to nthmemory cells MC1 to MCn, a pipe transistor PT, and at least one drainselect transistor DST.

The select transistors SST and DST and the memory cells MC1 to MCn mayhave structures similar to one another. In an embodiment, each of theselect transistors SST and DST and the memory cells MC1 to MCn mayinclude a channel layer, a tunneling insulating layer, a charge storagelayer, and a blocking insulating layer. In an embodiment, a pillar forproviding the channel layer may be provided in each cell string. In anembodiment, a pillar for providing at least one of the channel layer,the tunneling insulating layer, the charge storage layer, and theblocking insulating layer may be provided in each cell string.

The source select transistor SST of each cell string is coupled betweena common source line CSL and memory cells MC1 to MCp.

In an embodiment, the source select transistors of cell strings arrangedon the same row are coupled to a source select line extending in the rowdirection, and the source select transistors of cell strings arranged ondifferent rows are coupled to different source select lines. In FIG. 9,the source select transistors of the cell strings CS11 to CS1 m on afirst row are coupled to a first source select line SSL1. The sourceselect transistors of the cell strings CS21 to CS2 m on a second row arecoupled to a second source select line SSL2.

In another embodiment, the source select transistors of the cell stringsCS11 to CS1 m and CS21 to CS2 m may be commonly coupled to one sourceselect line.

The first to nth memory cells MC1 to MCn of each cell string are coupledbetween the source select transistor SST and the drain select transistorDST.

The first to nth memory cells MC1 to MCn may be divided into first topth memory cells MC1 to MCp and a (p+1)th to nth memory cells MCp+1 toMCn. The first to pth memory cells MC1 to MCp are sequentially arrangedin a −Z direction, and are coupled in series between the source selecttransistor SST and the pipe transistor PT. The (p+1)th to nth memorycells MCp+1 to MCn are sequentially arranged in the +Z direction, andare coupled in series between the pipe transistor PT and the drainselect transistor DST. The first to pth memory cells MC1 to MCp and the(p+1)th to nth memory cells MCp+1 to MCn are coupled through the pipetransistor PT. Gates of the first to nth memory cells MC1 to MCn of eachcell string are coupled to first to nth word lines WL1 to WLn,respectively.

A gate of the pipe transistor PT of each cell string is coupled to apipe line PL.

The drain select transistor DST of each cell string is coupled between acorresponding bit line and the memory cells MCp+1 to MCn. Cell stringsarranged in the row direction are coupled to a drain select lineextending in the row direction. The drain select transistors of the cellstrings CS11 to CS1 m on the first row are coupled to a first drainselect line DSL1. The drain select transistors of the cell strings CS21to CS2 m on the second row are coupled to a second drain select lineDSL2.

Cell strings arranged in the column direction are coupled to a bit lineextending in the column direction. In FIG. 9, the cell strings CS11 andCS21 on a first column are coupled to a first bit line BL1. The cellstrings CS1 m and CS2 m on an mth column are coupled to an mth bit lineBLm.

Memory cells coupled to the same word line in the cell strings arrangedin the row direction constitute one page. For example, memory cellscoupled to the first word line WL1 in the cell strings CS11 to CS1 m onthe first row constitute one page. Memory cells coupled to the firstword line WL1 in the cell strings CS21 to CS2 m on the second rowconstitute another page. As any one of the drain select lines DSL1 andDSL2 is selected, cell strings arranged in one row direction may beselected. As any one of the word lines WL1 to WLn is selected, one pagemay be selected in the selected cell strings.

In another embodiment, even bit lines and odd bit lines may be providedinstead of the first to mth bit lines BL1 to BLm. In addition,even-numbered cell strings among the cell strings CS11 to CS1 m or CS21to CS2 m arranged in the row direction may be coupled to the even bitlines, respectively, and odd-numbered cell strings among the cellstrings CS11 to CS1 m or CS21 to CS2 m arranged in the row direction maybe coupled to the odd bit lines, respectively.

In an embodiment, at least one of the first to nth memory cells MC1 toMCn may be used as a dummy memory cell. For example, the dummy memorycell(s) may be provided to decrease an electric field between the sourceselect transistor SST and the memory cells MC1 to MCp. Alternatively,the dummy memory cell(s) may be provided to decrease an electric fieldbetween the drain select transistor DST and the memory cells MCp+1 toMCn. When a larger number of dummy memory cells are provided, thereliability of an operation of the memory block BLKa is improved. On theother hand, the size of the memory block BLKa is increased. When asmaller number of dummy memory cells are provided, the size of thememory block BLKa is decreased. On the other hand, the reliability of anoperation of the memory block BLKa may be deteriorated.

In order to efficiently control the dummy memory cell(s), the dummymemory cell(s) may have a required threshold voltage. Before or after anerase operation of the memory block BLKa, a program operation may beperformed on all or some of the dummy memory cells. When an eraseoperation is performed after the program operation is performed, thethreshold voltage of the dummy memory cells control a voltage applied tothe dummy word lines coupled to the respective dummy memory cells, sothat the dummy memory cells can have the required threshold voltage.

FIG. 10 is a circuit diagram illustrating another embodiment BLKb of theone memory block among the memory blocks BLK1 to BLKz of FIG. 8.

Referring to FIG. 10, the memory block BLKb may include a plurality ofcell strings CS11′ to CS1 m′ and CS21′ to CS2 m′. Each of the pluralityof cell strings CS11′ to CS1 m′ and CS21′ to CS2 m′ extends along the +Zdirection. Each of the plurality of cell strings CS11′ to CS1 m′ andCS21′ to CS2 m′ includes at least one source select transistor SST,first to nth memory cells MC1 to MCn, and at least one drain selecttransistor DST, which are stacked on a substrate (not shown) under thememory block BLKb.

The source select transistor SST of each cell string is coupled betweena common source line CSL and the memory cells MC1 to MCn. The sourceselect transistors of cell strings arranged on the same row are coupledto the same source select line. The source select transistors of thecell strings CS11′ to CS1 m′ arranged on a first row are coupled to afirst source select line SSL1. Source select transistors of the cellstrings CS21′ to CS2 m′ arranged on a second row are coupled to a secondsource select line SSL2. In another embodiment, the source selecttransistors of the cell strings CS11′ to CS1 m′ and CS21′ to CS2 m′ maybe commonly coupled to one source select line.

The first to nth memory cells MC1 to MCn of each cell string are coupledin series between the source select transistor SST and the drain selecttransistor DST. Gates of the first to nth memory cells MC1 to MCn arecoupled to first to nth word lines WL1 to WLn, respectively.

The drain select transistor DST of each cell string is coupled between acorresponding bit line and the memory cells MC1 to MCn. The drain selecttransistors of cell strings arranged in the row direction are coupled toa drain select line extending in the row direction. The drain selecttransistors of the cell strings CS11′ to CS1 m′ on the first row arecoupled to a first drain select line DSL1. The drain select transistorsof the cell strings CS21′ to CS2 m′ on the second row are coupled to asecond drain select line DSL2.

Consequently, the memory block BLKb of FIG. 10 has a circuit similar tothat of the memory block BLKa of FIG. 9, except that the pipe transistorPT is excluded from each cell string in FIG. 10.

In another embodiment, even bit lines and odd bit lines may be providedinstead of the first to mth bit lines BL1 to BLm. In addition,even-numbered cell strings among the cell strings CS11′ to CS1 m′ orCS21′ to CS2 m′ arranged in the row direction may be coupled to the evenbit lines, respectively, and odd-numbered cell strings among the cellstrings CS11′ to CS1 m′ or CS21′ to CS2 m′ arranged in the row directionmay be coupled to the odd bit lines, respectively.

In an embodiment, at least one of the first to nth memory cells MC1 toMCn may be used as a dummy memory cell. For example, the dummy memorycell(s) may be provided to decrease an electric field between the sourceselect transistor SST and the memory cells MC1 to MCp. Alternatively,the dummy memory cell(s) may be provided to decrease an electric fieldbetween the drain select transistor DST and the memory cells MCp+1 toMCn. When a larger number of dummy memory cells are provided, thereliability of an operation of the memory block BLKb is improved. On theother hand, the size of the memory block BLKb is increased. When asmaller number of dummy memory cells are provided, the size of thememory block BLKb is decreased. On the other hand, the reliability of anoperation of the memory block BLKb may be deteriorated.

In order to efficiently control the dummy memory cell(s), the dummymemory cell(s) may have a required threshold voltage. Before or after anerase operation of the memory block BLKb, a program operation may beperformed on all or some of the dummy memory cells. When an eraseoperation is performed after the program operation is performed, thethreshold voltage of the dummy memory cells control a voltage applied tothe dummy word lines coupled to the respective dummy memory cells, sothat the dummy memory cells can have the required threshold voltage.

FIG. 11 is a block diagram illustrating a memory system 1000 includingthe memory device 100 of FIG. 7.

Referring to FIG. 11, the memory system 1000 includes a memory device100 and the controller 1100.

The memory device 100 may be configured and operated as described withreference to FIG. 7. Accordingly, overlapping description is omittedbelow.

The controller 1200 is coupled to a host (Host) and the memory device100. The controller 1200 is configured to access the memory device 100in response to a request from the host. For example, the controller 1200is configured to control read, write, erase, and background operationsof the memory device 100. The controller 1200 is configured to providean interface between the memory device 100 and the host. The controller1200 is configured to drive firmware for controlling the memory device100.

The controller 1200 includes a random access memory (RAM) 1210, aprocessing unit 1220, a host interface 1230, a memory interface 1240,and an error correction block 1250.

The RAM 1210 is used as at least one of a working memory of theprocessing unit 1220, a cache memory between the memory device 100 andthe host, and a buffer memory between the memory device 100 and thehost.

The processing unit 1220 controls overall operations of the controller1200.

The host interface 1230 includes a protocol for exchanging data betweenthe host and the controller 1200. In an embodiment, the controller 1200is configured to communicate with the host through at least one ofvarious interface protocols such as a universal serial bus (USB)protocol, a multimedia card (MMC) protocol, a peripheral componentinterconnection (PCI) protocol, a PCI-express (PCI-E) protocol, anadvanced technology attachment (ATA) protocol, a serial-ATA protocol, aparallel-ATA protocol, a small computer small interface (SCSI) protocol,an enhanced small disk interface (ESDI) protocol, an integrated driveelectronics (IDE) protocol, and a private protocol.

The memory interface 1240 interfaces with the memory device 100. Forexample, the memory interface 1240 may include a NAND interface or a NORinterface.

The error correction block 1250 is configured to detect and correct anerror of data received from the memory device 100 by using an errorcorrection code (ECC).

The controller 1200 and the memory device 100 may be integrated into onesemiconductor device. In an embodiment, the controller 1200 and thememory device 100 may be integrated into a single semiconductor deviceto constitute a memory card such as a PC card (personal computer memorycard international association (PCMCIA)), a compact flash (CF) card, asmart media card (SM or SMC), a memory stick, a multimedia card (MMC,RS-MMC or MMCmicro), an SD card (SD, miniSD, microSD or SDHC), or auniversal flash storage (UFS).

The controller 1200 and the memory device 100 may be integrated into asingle semiconductor device to constitute a semiconductor drive (solidstate drive (SSD)), which may be configured to store data in asemiconductor memory. If the memory system 1000 is used as thesemiconductor drive SSD, the operating speed of the host coupled to thememory system 1000 can be remarkably improved.

As another example, the memory system 1000 may be provided as one ofvarious components of an electronic device such as a computer, an ultramobile PC (UMPC), a workstation, a net-book, a personal digitalassistant (PDA), a portable computer, a web tablet, a wireless phone, amobile phone, a smart phone, an e-book, a portable multimedia player(PMP), a portable game console, a navigation system, a black box, adigital camera, a 3-dimensional television, a digital audio recorder, adigital audio player, a digital picture recorder, a digital pictureplayer, a digital video recorder, a digital video player, a devicecapable of transmitting/receiving information in a wireless environment,one of various electronic devices that constitute a home network, one ofvarious electronic devices that constitute a computer network, one ofvarious electronic devices that constitute a telematics network, an RFIDdevice, or one of various components that constitute a computing system.

In an embodiment, the memory device 100 or the memory system 1000 may bepackaged in various forms such as package on package (PoP), ball gridarrays (BGAs), chip scale packages (CSPs), plastic leaded chip carrier(PLCC), plastic dual in-line package (PDIP), die in Waffle pack, die inwafer form, chip on board (COB), ceramic dual in-line package (CERDIP),plastic metric quad flat pack (MQFP), thin quad flat pack (TQFP), smalloutline integrated circuit (SOIC), shrink small outline package (SSOP),thin small outline package (TSOP), thin quad flat pack (TQFP), system inpackage (SIP), multi-chip package (MCP), wafer-level fabricated package(WFP), or wafer-level processed stack package (WSP).

FIG. 12 is a block diagram illustrating an application example 2000 ofthe memory system 1000 of FIG. 11.

Referring to FIG. 12, the memory system 2000 includes a memory device2100 and a controller 2200. The memory device 2100 includes a pluralityof semiconductor memory chips. The plurality of semiconductor memorychips are divided into a plurality of groups.

In FIG. 12, it is illustrated that the plurality of groups communicatewith the controller 2200 through first to kth channels CH1 to CHk. Eachsemiconductor memory chip may be configured and operated identically tothe memory device 100 described with reference to FIG. 7.

Each group is configured to communicate with the controller 2200 throughone common channel. The controller 2200 is configured similarly to thecontroller 1200 described with reference to FIG. 11. The controller 2200is configured to control the plurality of memory chips of the memorydevice 2100 through the plurality of channels CH1 to CHk.

In FIG. 12, it has been illustrated that a plurality of semiconductormemory chips are coupled to one channel. However, it will be understoodthat the memory system 2000 may be modified such that one semiconductormemory chip is coupled to one channel.

FIG. 13 is a block diagram illustrating a computing system 3000including the memory system 2000 described with reference to FIG. 12.

Referring to FIG. 13, the computing system 3000 includes a centralprocessing unit (CPU) 3100, a RAM 3200, a user interface 3300, a powersupply 3400, a system bus 3500, and the memory system 2000.

The memory system 2000 is electrically coupled to the CPU 3100, the RAM3200, the user interface 3300, and the power supply 3400 through thesystem bus 3500. Data supplied through user interface 3300 or dataprocessed by the CPU 3100 are stored in the memory system 2000.

In FIG. 13, it is illustrated that the semiconductor memory device 2100is coupled to the system bus 3500 through the controller 2200. However,the semiconductor memory device 2100 may be directly coupled to thesystem bus 3500. In this case, the function of the controller 2200 maybe performed by the CPU 3100 and the RAM 3200.

In FIG. 13, it is illustrated that the memory system 2000 described withreference to FIG. 12 is provided. However, the memory system 2000 may bethe memory system 1000 described with reference to FIG. 11. In anembodiment, the computing system 3000 may be configured to include boththe memory systems 1000 and 2000 described with reference to FIGS. 11and 12.

According to the present disclosure, a low voltage detection circuithaving accurate detection performance and a memory device including thesame are provided.

Various embodiments have been disclosed herein, and although specificterms are employed, they are used and are to be interpreted in a genericand descriptive sense and not for purpose of limitation, In someinstances, as would be apparent to one of ordinary skill in the art asof the filing of the present application, features, characteristics,and/or elements described in connection with a particular embodiment maybe used singly or in combination with features, characteristics, and/orelements described in connection with other embodiments unless otherwisespecifically indicated. Accordingly, it will be understood by those ofskill in the art that various changes in form and details may be madewithout departing from the spirit and scope of the present disclosure asset forth in the following claims.

What is claimed is:
 1. A low voltage detection circuit comprising: acomparison voltage generator configured to generate a first comparisonvoltage and a second comparison voltage having a level higher than thatof the first comparison voltage by dividing a power voltage; a firstcomparator configured to output a low voltage detection enable signal bycomparing the first comparison voltage with a reference voltage; asecond comparator configured to output a detection signal by comparingthe second comparison voltage with the reference voltage while the lowvoltage detection enable signal is being input; a detection signalmaintainer configured to provide a low voltage detection signal to anoutput terminal according to the detection signal; and an output signaldischarger configured to discharge the low voltage detection signalaccording to the low voltage detection enable signal.
 2. The low voltagedetection circuit of claim 1, further comprising a voltage providerconfigured to provide the power voltage to the comparison voltagegenerator.
 3. The low voltage detection circuit of claim 1, wherein thefirst comparator outputs the low voltage detection enable signal to havea logic high level when the first comparison voltage is lower than thereference voltage, and outputs the low voltage detection enable signalto have a logic low level when the first comparison voltage is greaterthan or equal to the reference voltage.
 4. The low voltage detectioncircuit of claim 1, wherein the second comparator outputs the detectionsignal to have the logic high level when the second comparison voltageis lower than the reference voltage, and outputs the detection signal tohave the logic low level when the second comparison voltage is greaterthan or equal to the reference voltage.
 5. The low voltage detectioncircuit of claim 1, wherein the sensing signal maintainer outputs thelow voltage detection signal to have the logic high level when thesensing signal is changed from the logic low level to the logic highlevel, and maintains the low voltage detection signal having the logichigh level when the sensing signal is changed from the logic high levelto the logic low level.
 6. The low voltage detection circuit of claim 1,wherein the output signal discharger discharges the low voltagedetection signal provided to the output terminal when the low voltagedetection enable signal is changed from the logic high level to thelogic low level.
 7. The low voltage detection circuit of claim 1,further comprising a delay circuit configured to delay the low voltagedetection enable signal output by the first comparator and then providethe delayed low voltage detection enable signal to the secondcomparator.
 8. The low voltage detection circuit of claim 1, wherein thecomparison voltage generator includes a plurality of resistors, and thefirst comparison voltage and the second comparison voltage arerespectively output at preselected nodes between the plurality ofresistors.
 9. A memory device comprising: a memory cell array includinga plurality of memory cells; a voltage generator configured to generatean operation voltage to be supplied to the plurality of memory cells;and control logic configured to provide the operation voltage to theplurality of memory cells or discharge the provided operation voltage,wherein the voltage generator further includes a low voltage detectioncircuit configured to output a low voltage detection signal to thecontrol logic when a power voltage input from the outside corresponds toa low voltage state, wherein the low voltage detection circuit includes:a comparison voltage generator configured to generate a first comparisonvoltage and a second comparison voltage having a level higher than thatof the first comparison voltage by dividing the power voltage; a firstcomparator configured to output a low voltage detection enable signal bycomparing the first comparison voltage with a reference voltage; asecond comparator configured to output a detection signal by comparingthe second comparison voltage with the reference voltage while the lowvoltage detection enable signal is being input; a detection signalmaintainer configured to provide a low voltage detection signal to anoutput terminal according to the detection signal; and an output signaldischarger configured to discharge the low voltage detection signalaccording to the low voltage detection enable signal.
 10. The memorydevice of claim 9, wherein the low voltage detection circuit furtherincludes a voltage provider configured to the power voltage to thecomparison voltage generator.
 11. The memory device of claim 9, whereinthe first comparator outputs the low voltage detection enable signal tohave a logic high level when the first comparison voltage is lower thanthe reference voltage, and outputs the low voltage detection enablesignal to have a logic low level when the first comparison voltage isgreater than or equal to the reference voltage.
 12. The memory device ofclaim 9, wherein the second comparator outputs the detection signal tohave the logic high level when the second comparison voltage is lowerthan the reference voltage, and outputs the detection signal to have thelogic low level when the second comparison voltage is greater than orequal to the reference voltage.
 13. The memory device of claim 9,wherein the detection signal maintainer outputs the low voltagedetection signal to have the logic high level when the detection signalis changed from the logic low level to the logic high level, andmaintains the low voltage detection signal having the logic high levelwhen the detection signal is changed from the logic high level to thelogic low level.
 14. The memory device of claim 9, wherein the outputsignal discharger discharges the low voltage detection signal providedto the output terminal when the low voltage detection enable signal ischanged from the logic high level to the logic low level.
 15. The memorydevice of claim 9, wherein the low voltage detection circuit furtherincludes a delay circuit configured to delay the low voltage detectionenable signal output by the first comparator and then provide thedelayed low voltage detection enable signal to the second comparator.16. A memory device comprising: a memory cell array; a low voltagedetector configured to generate, while a first comparison voltage islower than a reference voltage, a detection signal when a secondcomparison voltage becomes lower than the reference voltage or when thesecond comparison voltage then becomes higher than the referencevoltage; and control logic configured to discharge an operation voltageto the memory cell array according to the detection signal, wherein thefirst and second comparison voltages are divided from a power voltage,and wherein the first comparison voltage is lower than the secondcomparison voltage.